The present invention relates to intravascular guide wires and methods of use thereof. In particular, the present invention relates to an intravascular guide wire and methods of use to facilitate catheter exchange thereover.
One common use for guide wires is in coronary angioplasty which is a treatment for obstructive coronary artery disease. Obstructive coronary artery disease continues to be a serious health problem facing our society today. This disease is the result of the deposit of fatty substances on the interior of the walls of the arteries. The build-up, or lesion, of such deposits results in a narrowing of the inside diameter of the artery which in turn restricts the blood flow through the artery. This condition, wherein the opening of the artery is narrowed, is known as stenosis. Coronary artery bypass graft surgery may be used to treat this disease. Bypass surgery, however, may be extremely invasive and traumatic to the patent. Angioplasty is a less invasive and traumatic treatment for obstructive coronary artery disease.
Angioplasty is a procedure in which a balloon is positioned on the inside of the artery at the site of the lesion and expanded. In this procedure, an expandable balloon is attached to the distal end of a small diameter catheter which includes means for inflating the balloon from the proximal end of the catheter. The catheter is maneuvered or steered through the patent's vessels to the site of the lesion with the balloon in an uninflated form. When the uninflated balloon is properly positioned at the lesion, the balloon is then inflated to dilate the restricted area. The expansion of the balloon thus opens the restricted area of the artery.
One of the tasks associated with the positioning of the catheter is steering it through the blood vessels until it reaches the desired location. In order to accomplish this task, a guide wire may be used that is typically thinner than the catheter and easier to maneuver. Once the guide wire is inserted in the desired blood vessel and positioned across the stenosis, the catheter is slid over the guide wire, e.g. coaxially. The opening of the catheter that the guide fits coaxially within is commonly called a lumen.
Guide wires employed in coronary angioplasty are usually of relatively small diameter due to the combination of the small size of the relevant blood vessels and the even smaller size of the luminal openings of the dilatation catheter. Guide wires of a very small diameter, for example 0.010 to 0.018 inches, may be suitable for use in the narrow coronary vessels. Such guide wires may have an extremely floppy distal tip which may be bent or preformed by the physician to facilitate placement of the guide wire at the desired location.
Typically, a guide wire is longer than the catheter with which it is used for at least two reasons. First, at least a portion of the distal end of the guide wire extends past and through the distal end of the catheter. This distal end of the guide wire is usually much narrower and more flexible than the catheter, and may be biased in a preselected direction. This assists the physician in steering the catheter through the patient's vasculature.
Second, the proximal end of the guide wire extends outwardly from the proximal portion of the catheter. During a procedure, both the proximal ends of the guide wire and the catheter remain outside the patient's body. The physician can steer the guide wire by torsionally rotating the proximal end of the guide wire. A portion of the proximal portion of the guide wire may also be advanced into or extracted from the catheter to either increase or decrease the amount of the guide wire extending from the distal portion of the catheter. Again, this extra length extending from the distal end of the catheter may allow the physician to better steer the guide wire or place it through narrower regions of the patient's vasculature. In coronary angioplasty, the catheter may be 135 centimeters long while the guide wire may be 175 centimeters long.
A problem associated with the use of guide wires, especially in the coronary vasculature, relates to exchanging catheters after the guide wire and catheter have already been inserted into the patient's body. An exchange may be required when, after the physician has placed one catheter into the patient, the physician determines that a different size catheter is needed. For example in coronary angioplasty, after steering the catheter substantially to the stenosis, the physician may find that the balloon selected is too large or too small. An exchange may also be needed to replace a balloon dilatation catheter with a different intravascular device, such as an atherectomy cutter, a stent, a diagnostic ultrasound catheter, etc. This may occur even after the guide wire is within the stenosed area. When an exchange is made, it is highly desirable that the guide wire remain in place. This prevents the physician from having to withdraw the guide wire, "re-steer" it through the patient's vasculature and cross the lesion again.
One way to affect a change without losing the positioning of the guide wire is for the physician to remove the existing guide wire while leaving the catheter in place and then replacing the existing guide wire with an exchange wire. The exchange wire is typically much longer than the original guide wire. For example, it may be 300 centimeters long. Once the exchange wire is in place, the physician removes the catheter from the patient over the exchange wire. While removing the catheter, the physician holds the proximal end of the exchange wire in place so that the distal end of the wire remains in the same position inside the patient's body. Without the longer exchange wire, the physician would have no way of holding the guide wire when removing the catheter, because the proximal end of the normal length guide wire would soon disappear into the catheter as the catheter was being extracted from the patient's body.
One disadvantage to this prior art method is that it takes time to change guide wires. Furthermore, the physician must again insert the distal-most tip of the exchange wire into the exact position desired. This is necessary because, as stated above, the distal end of the guide wire typically extends from the distal end of the catheter to "guide" the catheter. Each time the physician must reinsert the guide wire, there may be a risk of injury to the patient's vasculature. Also, this process of reinserting the distal end of the guide wire may be time consuming.
Although one solution to this problem might be to use a longer (for example double-length) guide wire in the first place, this also may pose a problem for the physician. For instance, the excess wire extending from the proximal end of the catheter may make it difficult to torsionally rotate the wire and steer it through the patient's vasculature.
U.S. Pat. No. 4,919,103 (Gambale et al.) attempts to solve these problems by providing a guide wire extension that is crimped onto a regular guide wire when needed. One disadvantage of this prior art is that, once crimped on, the extension is permanently attached to the guide wire. This permanent attachment causes similar disadvantages with maneuvering as expressed above with respect to the longer, one piece exchange wire.
Certain detachable and extendable guide wires have also been available. A disadvantage of some of these guide wire extension designs is that it can be time consuming and tedious to connect an extension wire and then disconnect it after use.
Therefore, there is a need to provide a guide wire that provides adequate length for the purpose of exchanging catheters, while at the same time allowing the physician to steer the portion of the guide wire that is within the patient's body easily by torsional rotation from a proximal location.
Also, there is a need for a guide wire that has qualities that are desirable among guide wires generally, and that is also able to make the exchange of catheters easier. It is also desired that a longer guide wire that is still easy to steer be provided.